The present invention relates to apparatus for damping torsional vibrations. Such apparatus can be utilized with advantage in composite masses or flywheels which are installed in the power trains of motor vehicles to transmit torque between a prime mover (e.g., a combustion engine) and a driven unit (e.g., a manually shiftable, automated or automatic transmission). More particularly, the invention relates to improvements in apparatus wherein torque is being transmitted between an output member (such as a member including a primary mass or flywheel of a composite mass or flywheel) and an input member (such as a member including a secondary mass or flywheel of the composite mass or flywheel) by way of one or more resilient elements which permit angular movements of the output and input members relative to each other.
U.S. Pat. Nos. 1,541,748 (granted Jun. 9, 1925 to Davis) and 1,997,021 (granted Apr. 9, 1935 to Spase) disclose cushioning or vibration damping apparatus wherein one or more springs extend around the common axis of the rotary input and output members. One end portion of each spring is form-lockingly connected with the input member, and the other end portion of each such spring is form-lockingly connected with the output member. A drawback of such apparatus is that they prevent rotation of the input and output members relative to each other beyond a predetermined angle regardless of the magnitude of transmitted torque and irrespective of the circumstances of use of the patented apparatus.